This study is directed at examination of the early stages of carbohydrate metabolism in the gram-positive homofermentative oral microflora. Glucokinase and fructokinase from Streptococcus mutans have been purified to homogeneity and biochemically characterized. Since this species has been shown to transport sucrose via a PEP:PTS system, the physiological importance of these enzymes remains to be established. Sucrose-6-phosphate has been synthesized and its biological activity examined. The role of plasmids in potentiating carbohydrate utilization in these organisms is also under study. Techniques for the elimination of plasmids from lactobacilli have been developed. Using these techniques to generate plasmid-variants, it has been demonstrated that lactose metabolism in Lactobacillus casei DR1002 is plasmid-associated. The possibility that sucrose metabolism in L. casei DR1004 may be similarly plasmid-mediated is under investigation.